The invention relates to a strut bearing comprising two bearing races, roll bodies arranged between these races, and a seal which seals the space between said two races.
Strut bearings of this type serve for supporting strut-type wheel suspensions for the steerable wheels of automotive vehicles on the vehicle body. The strut-type suspension is essentially formed by a shock absorber and a helical spring surrounding the same. The head of the shock absorber is connected to the vehicle body and is surrounded by the strut bearing. The casing of the strut bearing must, accordingly, have a relatively large internal diameter. A member rigidly connected to the vehicle body is supported on the upper race of the bearing, whereas the lower race is supported on a spring collar which forms an engagement surface for the upper end of the helical spring. Thus, the bearing must be capable of absorbing a high axial load which corresponds to the portion of the weight of the vehicle acting upon the associated wheel. In addition, the bearing is subject to relatively high radial forces, because the strut is normally inclined relative to the vertical.
Known strut bearings of this type comprise a casing formed by two annular casing halves made of synthetic resin and snap-fastened to one another, which accommodate the races of the bearing and on which the seal is formed. In view of the relatively high load, a comparatively hard synthetic resin material must be used for the casing. The seal is formed by sealing lips formed integrally with the casing halves or by labyrinth profiles and has the purpose to protect the races and roll bodies accommodated in the casing against mud and water.
When the vehicle wheel is steered, the bearing is expected to allow for a smooth rotation of the strut about its longitudinal axis.
In conventional strut bearings, it may however happen during a steering operation that the bearing becomes locked, so that the rotation of the spring collar is stopped and the helical disk is subject to a torsional force. When the torsional force exceeds the locking force of the spring collar, the spring collar makes an abrupt rotation, and the torsional bias of the helical spring is released, until the bearing locks again. This effect which is also termed "spring jumping" is perceptible to the driver as a slight vibration and a disturbing noise during the steering operation.
It is an object of the invention to provide a strut bearing which can avoid the phenomenon of spring jumping.